WASHINGTON — If there ever was any doubt, the Senate is offering even more evidence that 2010 is going to be a nasty election year.

After months of Republican attacks during the health care debate, Democrats gained a measure of revenge with a three-day pounding on the GOP for blocking financial reform.

Senate Republicans finally surrendered, and debate on how to rein in Wall Street began last week. But if health care reform was a vicious partisan struggle over who championed the little guy, this fight could be populism on steroids.

“On every issue, both parties are seeking to align themselves with the average voter,” said Jennifer Duffy, a Senate analyst with the nonpartisan Cook Political Report. “Wall Street, in particular, as an issue speaks to a ‘them versus us’ argument. I’m not sure any politician wants to be on the side of Wall Street.”

And that might not be the only debate to influence the midterm elections. There’s a push among some Democrats to also tackle immigration — especially in light of Arizona’s controversial new “show me your papers” law — or climate change, or both.

If you’ve got the political capital, the argument goes, use it before you lose it. In other words, given the anti-Washington mood, pundits say Democrats and President Barack Obama should take advantage of their House and Senate majorities while they still have them.

Who knows what the political breakdown on Capitol Hill will look like after Nov. 2? Unfortunately for Democrats, issues such as immigration and climate change are highly radioactive.

Democratic pollster Doug Schoen recently wrote that both were “clear losers politically at this time.” He said Democrats in Congress instead should focus solely on jobs, “or face the prospect of an overwhelming defeat in November.”

Even Republican Sen. Pat Roberts of Kansas, normally not in the business of advising the opposition, questioned the wisdom of tackling so many complex, hot-button issues in an election year — especially when so many voters are hurting financially, and so many don’t trust Washington to fix the problems.

“After health care, why on earth would you want to bring those two up, while on the front burner we have financial regulatory reform?” Roberts said. “That bill in itself is 1,500 pages long.”

The political mood right now favors the Republicans, though all “incumbents are in more trouble than at any time,” said Burdett Loomis, who teaches politics at the University of Kansas.

Republican Sen. Sam Brownback of Kansas, who is leaving Capitol Hill to run for governor, said that he has encountered “a lot of anxiousness and anger toward Washington” as he campaigns around his state.

He said the Senate should draw a lesson from the health reform debate and simplify any big-ticket bills that it takes up: Wall Street reform should just focus on market transparency and whether some firms are “too big to fail.”

Climate change legislation also should give way for the time being to a renewable energy bill, and immigration reform without first controlling the southern border is a “mockery,” Brownback said.

Democrats are still reeling from the long, bitter battle over health reform, which not a single Republican in either chamber voted for. It handed the GOP a ready-made political message.

Republicans also are — to borrow Obama’s 2008 campaign chant — more “fired up, ready to go.” A recent Gallup Poll found that the GOP held a 20-point advantage — 57 percent to 37 percent — among voters who are “very enthusiastic” about voting in the midterm elections.

Duffy said Democrats need to wake up their base. Issues such as immigration and climate change energize the activists on both sides who show up at rallies and register voters and make phone calls to get them out on Election Day.

A potential partisan battle this summer over the president’s Supreme Court nominee could help, too, as well as each side claiming the moral high ground in trying to fix Wall Street.

“I have real concerns that in its current form, the Democrats’ bill is a massive government overreach that will punish Main Street, hurt families and cost jobs by stifling small businesses and entrepreneurs,” Republican Sen. Kit Bond of Missouri said on the Senate floor.

“Republicans want to ensure that we fix Wall Street without crippling Main Street.”

She said in an interview that Republicans attacked Democrats during the health reform debate for a lack of transparency in negotiations. But they held up debate last week on Wall Street reform in favor of working out a compromise in private, she said.

“If they were helping ‘Main Street,’ why would they need doors to be closed?” McCaskill asked. “Are we to believe they’re going to go to bat for the little guy?”

With the political rhetoric and passions already ramped up and the election still seven months off, should her party push ahead on other controversial issues?

“I don’t know about the politics of it,” McCaskill said. “I know there are big problems and we have to keep working on all of them. I’m trying to keep my head down.”